A voltage management system (VMS) is a control system enhancing voltage stability of an electrical power grid by using generators of the electrical power grid. Each of the generators distributes reactive power generation on the basis of each generator's own ability to generate power. The voltage management system calculates electrical distances to buses of the electrical power grid, and selects target buses for measuring changes of all voltages. That is, the voltage management system controls the reactive power generation of the generators so as to maintain levels of voltages of the target buses.
In order to control reactive power generation, the voltage management system includes a fast response type voltage control unit (continuous voltage controller: CVC), a static voltage control unit (discrete voltage controller: DVC), and a reactive power distributor (reactive power dispatcher: RPD).
The fast response type voltage control unit and the static voltage control unit respectively generate a control signal controlling reactive power of the generator and a control signal controlling reactive power of phase modifying equipment. The fast response type voltage control unit provides a reference value of the reactive power generation, which is required to be outputted by each of the generators, by using voltage differences of the target buses. The reference value of the reactive power generation is provided to an automatic voltage adjustment device (automatic voltage regulator: AVR) by being converted through the reactive power distributor mounted in the generator. The automatic voltage adjustment device controls the reactive power generation of the generators by using a signal received from the reactive power distributor. That is, the voltage management system distributes the reactive power by being connected to the electrical power grid online, thereby enhancing voltage stability.
However, without the voltage management system, the generators output reactive power by using respective automatic voltage adjustment devices. Therefore, the generators output generated reactive power that is completely unrelated to the control signals of the voltage management system. Therefore, in a conventional case, when the voltage management system is initially applied to the electrical power grid or the voltage management system is replaced, it is required to set a reference value of an initial reactive power generation, otherwise, a transient phenomena occurs in the electrical power grid.
In addition, when the voltage management system is manually operated, it is difficult to provide an optimum control signal to the electrical power grid.
In this regard, there is Korean Patent Application Publication No. 10-2005-0107972, titled “System and method for calculating real-time voltage stability risk index in power system using time series data.”